1. Field of the Invention
The present invention relates to a mobile communication network system configured by a plurality of mobile communication systems.
2. Description of the Related Art
At the present, a mobile communication system for a cellular phone etc. shifts from a second generation system such as a PDC (Personal Digital Cellular) method to a third generation system based on a CDMA (Code Division Multiple Access) method, wherein a variety of services based on the third generation system are started.
In this type of conventional mobile communication network system, the mobile communication systems are respectively provided according to the respective communication methods and individually need to grasp a location of a user terminal (mobile station). Such being the case, location information of the mobile station is registered with respect to each of the mobile communication system in a database called a home location register (which will hereinafter be also simply abbreviated to HLR) within the mobile communication network system. Further, the location of the mobile station (which will hereinafter be also simply abbreviated to MS) can be grasped according to a communication area of a base station (which will hereinafter be also simply be abbreviated to BS) installed in each cell, and therefore information about each base station has hitherto been employed for the location information of the mobile station.
Herein, a location registration procedure of the mobile station in the conventional mobile communication network system will be explained with reference to FIG. 11. FIG. 11 is a diagram showing a location registration sequence of the mobile station in the conventional system. In FIG. 11, MS represents the mobile station, BS 1 indicates a base station in a mobile communication system 1, BS 2 designates a base station in a mobile communication system 2, and HLR stands for the home location register. Further, the mobile communication system 1 is, e.g., the CDMA wireless system, the mobile communication system 2 is, e.g., the PDC wireless system, and the MS is the user terminal having wireless interface functions for both of the CDMA method and the PDC method. In this case, the MS is capable of performing the communications with both of the mobile communication system 1 and the mobile communication system 2, and hence the conventional system has a necessity of independently conducting location registration for each of the mobile communication system 1 and the mobile communication system 2.
On the other hand, a next generation mobile communication method enabling further high-speed wireless communications is now under examinations. Various categories of standards for this type of next generation mobile communication method are drawn up by 3GPP (3rd Generation Partnership Project). In particular, a technology related to a cell selection and a cell reselecting process in an idle mode procedure applied to the user terminal is disclosed in the following conventional Non-Patent document 1. The conventional Non-Patent document 1 is “User Equipment (UE) procedures in idle mode and procedures for cell reselection in connected mode (Release 5) (3GPP TS 25.304, 2005-03, V5.8.0.).”
In the conventional mobile communication network system shown in FIG. 11, a problem is that a dual-mode-supported mobile station needs to transmit radio waves for the location registration to each of the wireless systems and therefore consumes a large quantity of electric power.
On the other hand, in the next generation mobile communications, with a speedup in transmission rate and a cooperation of the plurality of wireless systems with each other, it is desirable to actualize such a system that users can utilize the wireless systems without being aware of these wireless systems in whatever environments. Then, it is considered that in the next generation mobile communications, the plurality of mobile communication systems are separately employed corresponding to applications of the users, and a mobile communication network taking a composite form of these systems will be configured.